The Zero-Length Launch Fighter

v1.0.3 / 01 oct 02 / greg goebel / public domain

* Many strange and interesting ideas have been pursued through the history
of aircraft development. None were much more strange than the "zero-length
launch (ZEL)" concept, in which a jet fighter was blasted off the back of a
truck with a solid-fuel rocket. This document describes the origins,
development, and ultimate fate of the ZEL concept.

* During the Cold War, the vulnerability of airfields to attack was obvious
to military planners, and a number of schemes were dreamt up to develop ways
to fly aircraft without using airfields. Early experiments with vertical
take-off and landing (VTOL) aircraft, the "flying pogos", focused on aircraft
that could take off straight up and land on their tails. Landing was a
frightening procedure and the concept did not inspire enthusiasm.

Another approach was considered: put a rocket on a conventional aircraft and
simply blast it into the sky, without need for a runway. "Jet-assisted
take-off (JATO)" rockets had been used to help get heavily-loaded aircraft
off the runway since the end of World War II, and developing a bigger rocket
to do the whole job didn't seem like too big a stretch. Besides, by 1953,
contemporary cruise missiles were being launched with precisely such a
technology.

The idea materialized in the form of a program named "Zero Length Launch /
Mat Landing (ZELMAL)". Not only would a Republic F-84G Thunderjet fighter be
blasted into the sky by a big booster rocket, the fighter would also land,
gear up, on a huge inflatable mat, 25 x 245 x 1 meters (80 x 800 x 3 feet) in
size, and snag an arresting cable to stop.

Tests were begun in December 1953 at Edwards Air Force Base in California.
Take-offs were surprisingly easy, but the mat landings were another matter.
The inflatable mat, which was transported on a couple of trailer trucks,
leaked the first time it was set up, and portions had to be sent back to
Goodyear, the manufacturer, for repairs.

The first mat landing didn't take place until 2 June 1954. It was a fiasco.
The F-84G's arresting hook tore up the mat, and the aircraft was so badly
damaged that it had to be written off. The test pilot, Robert Turner, was
laid up with back injuries for months. Two more mat landings were performed,
and though the results were nowhere near as bad as the first landing, the
idea was still clearly unworkable.

George Rodney, one of the test pilots, described the mat landings: "We tied
ourselves into the seat real well, so we wouldn't pitch forward into the
control column and the instrument panel, but unfortunately your head, it goes
into a big arc and comes down on your chest."

Rodney suffered a neck injury that bothers him to this day. ZELMAL was
terminated after 28 launches. "It needed some work, that was for damn sure,"
Rodney said later. The Air Force abandoned the concept for a time.

* Although the mat landings were a bad idea, the rocket take-offs had
actually worked pretty well, and in 1957 the Air Force decided to revive that
part of the concept. The idea was to launch a nuclear-armed strike aircraft
from a truck trailer, bomb a target, then have the pilot bail out over
friendly territory. The acronym was shortened to "ZEL".

The F-100 Super Sabre was selected for tests, which posed some problems. The
F-100 weighed over twice as much as the F-84, and required a really big
booster rocket to get it into the air. The booster was built by Rocketdyne
and generated almost 59,000 kilograms (130,000 pounds) of thrust for four
seconds, providing a maximum acceleration of 4 gees. The aircraft would be
instantly airborne and would be flying at an altitude of 120 meters (400
feet) and almost 450 KPH (275 MPH) at rocket burnout.

Engineers conducted preliminary launch tests with an "iron bird", a structure
of steel and concrete that simulated an F-100. The iron bird performed some
really impressive maneuvers, such as backward somersaults, that demonstrated
the importance of precisely aligning the booster.

The first actual shot with an F-100 went fine. The test pilot, a remarkably
laid-back guy named Al Blackburn, found it "exhilirating" and "better than
any ride you can find at Disneyland."

The second launch didn't go so well. The booster didn't separate, and
nothing Blackburn could do would shake it off. He had to eject and let the
aircraft crash into the desert. A post-mortem showed the booster had hung up
on the attachment bolts, which were supposed to shear off, but didn't. The
attachment scheme was modified with explosive charges that could blow the
bolts off on command.

Fourteen more flights were performed between March and October 1958. All
these shots went well, and became perfectly routine. One pilot performed a
ZEL launch for a public demonstration and did a slow roll immediately after
booster separation. There was no doubt of the technical feasibility of ZEL,
but by this time there were doubts that sending a nuclear-armed fighter
around the countryside on a truck was such a good idea. In consequence, a
few launches were performed from inside a hardened shelter at Holloman AFB in
New Mexico. There were no problems.

100 F-100s were modified for ZEL. In the early 1960s, the German Luftwaffe
sponsored similar launch experiments with their F-104 strike fighters.
Nothing came of any of it. Nobody wanted to field ZEL. The idea was sexy,
it worked well, but it was expensive, and had nasty logistical and security
concerns associated with it.

In the end, the capability offered by the system was provided by battlefield
missiles and the Harrier VTOL "jump-jet" that didn't need a booster rocket.
Nobody but test pilots ever blasted a jet fighter into the sky on a rocket
booster. It wasn't a practical idea, but it had certainly been a ride that
Disney could never have built in a thousand years.

* As was typical of the Cold War, what the Americans would do, the Soviets
would often do in response, and the reverse. It is therefore not surprising
that the Soviets performed ZEL experiments of their own, using their
counterpart to the American F-100, the MiG-19.

The Soviet motivation was different, however. Instead of dispersing
nuclear-armed strike aircraft to protect them from a first strike, the
Soviets wanted to launch air-defense interceptors from remote locations and
forward battle areas. The concept was suggested by the Mikoyan-Gurevich
(MiG) design bureau, and development of a trailer-launched MiG-19 system was
approved in 1955.

The result was a specially-built version of the MiG-19, designated the
"SM-30". The SM-30 was reinforced to allow it to tolerate the stresses of
rocket-boosted takeoff, incorporated a special headrest to protect the pilot
from whiplash, and replaced the single ventral fin of the MiG-19 by a pair of
fins straddling a PRD-22 solid-fuel booster. Like the F-100's booster
rocket, the PRD-22 generated about 59,000 kilograms (130,000 pounds) of
thrust.

The SM-30 was transported to a remote site on a large trailer, and then
placed on a separate trailer for launch. A trench had to be dug behind the
trailer to contain the exhaust, which would otherwise kick up a cloud of
debris that would be visible from far away. The aircraft was secured to the
launch rail by bolts that would, in principle, shear when afterburner was
engaged.

The first test launch, using a remote-controlled SM-30, was conducted in the
fall of 1956. The launch went smoothly, but the launch trailer was wrecked,
and so a blast shield was devised.

The first piloted launch was in April 1957, with test pilot Georgi M.
Shiyanov at the controls. Shiyanov had trained for the launch on a special
launch simulator catapult. He had endured 18 gees on one test when the
technician arming the catapult made an error. Shiyanov suffered no real harm
from the incident. Sources make no mention of any consequential harm to the
technician.

As with the American ZEL efforts, launches proved surprisingly easy.
Landings proved a bit trickier. The standard drag chute for the MiG-19
wasn't adequate for the rough forward-based landing strips envisioned for the
ZEL fighter, and so an arresting-cable scheme was implemented and partially
tested.

The tests were terminated when the Soviet government lost interest in the
concept, for reasons somewhat similar to those that killed the American ZEL
project. The requirement for a landing strip reduced the attractiveness of
ZEL, while attempting to transport such a big and bulky system across the
countryside was difficult, particularly when confronted by obstacles such as
tunnels. The development of effective battlefield surface-to-air missiles
proved to be a much more workable solution to the problem of forward air
defense, and the Soviet ZEL went nowhere.

"Runways Of Fire", by Ed Regis, SMITHSONIAN AIR & SPACE, October-November
1995, 68:76. The SMITHSONIAN also produced a video tape to go along with
the article, which has some splendid footage of ZEL take-offs, along with
a considerable amount of padding.

ZEL was one of those nifty ideas in circulation when I was a kid, in the
early 1960s, and reading the SMITHSONIAN article brought back memories that
inspired me to write this document.

Model kits were available not only for the F-100 ZEL concept, but for the
F-104 implementation as well. I even recall an episode of the old MAN FROM
UNCLE TV spy series in which a gang of terrorists attempted to seize a
nuclear-armed ZEL fighter hidden in an underground silo. Interestingly, I
recollect the head terrorist was Slim Pickens, immortalized for his role as
Major "King" Kong in Stanley Kubrick's movie DR. STRANGELOVE, riding an
H-Bomb to glory in one of cinema's most famous images.

Sometimes it's interesting find out what really happened to those crazy
ideas dreamed up decades ago that had their moment of fame, and then vanished
into the haze.